The analysis of sequence specific DNA binding proteins in Drosophila has been continued by this group. The heat shock activator protein is now routinely purified to homogeneity, and mouse antibodies against the protein have been prepared. This reagent will be extremely useful for further studies on the function of the protein, which pre-exists in normal cells, and is post-translationally modified in response to heat shock to be a sequence-specific binding protein. NFftz1, a nuclear protein found in Drosophila embryos, has been extensively purified and characterized biochemically. This protein may negatively regulate the transcriptional activity of the segmentation gene fushi tarazu.